What used to be one of my favorite ponds to fish, one that I pulled 3lbers out of in the dead of winter, has not been productive this summer. My first trip out there this summer I noticed a very unnatural blue/blue-green color to the water. I was told by a buddy it was an additive to control and kill the algae. It seems to have stayed a very similar color for most of the summer. Could this have caused the fish population to decrease?

What you have is blue-green algae.  It's pretty common, and usually isn't cause for concern so long as it's not a heavy bloom.  If it's really bad, than it could kill fish.

 

For more information on algae blooms and how to read them, see http://www.bassresource.com/fish_biology/algae-bloom-definition.html

Hello--- its from phosphorous from our lawns, animal waste, fertilizer (The Saltwater rivers are DYING) Indian river lagoon ) etc Google search for yourselves-- Doug really hated this and knew it was going there- but the powers that be in our states--- believe spraying, pellets, carp etc. are the answer--- CLEARLY THEY ARE NOT....  A real shame

The city puts a chemical in all the ponds it manages here in mesquite. It gave all the waters a bluish tint that was very noticeable when first introduced a few years back.

It could be a blue/green algae bloom. Sometimes it will even have a foam on top of the water that has a white milky look to it. Looks sort of like motor oil on top of the water floating. The wind will blow it to a corner somewhere and it usually wont last long. Not a bad thing.

 

 Or it could be an additive (Water Dye) which is not harmful to the fish. It darkens the water to restrict sunlight. This retards weed growth. If it was put into a lake after abundant weeds were present it could cause the weeds to dye that were already there and in turn deplete oxygen levels. If enough oxygen is depleted it could cause a fish kill.

My ol' ladys son works for an algae and mosquito control company. He went thru quite a bit of training, Keeping wildlife and fish healthy is their number one priority. Quite annoying when were out fishing and he's schooling me on different types of algae.  

My local pond has this too. I have heard from neighbors that it is mosquito killer and others say it is algae killer so I don't know which. It does kill fish. The population in my pond has gone down so far.. I have seen bass dead, and floating a day or two after the water turns blue. It might be fertilizers too cause people like on this pond and their lawns go up to the shore. I pretty much gave up on this pond cause I have only caught 2 out of it this year and they were both under 1/2 pound!

I have the same issue at my favourite pond. It used to be full of algae and I would have a blast catching fish, but now it's "under construction". All the weed is literally gone and there's a blue tint to the colour. I am assume, they put something in the water to control. BTW, fishing has been terrible.

There is an additive sold by our local fish hatchery that is like a die packet that is used to give the water a blue color and control algae.. I convinced my father to stop using it.. I read that it destroys the biodiversity of a pond and kills off the tiny organisms that make up the bottom of the ponds food chain.

of course, now he uses a different algae control that I suspect is leaving the pond very stained, there is almost no weed/algae growth which I believe is causing expedited bank erosion and muddy water.